Your second problem is here:
You are adding a force towards wherever the camera is pointing so if the camera is pointing backwards… well you go backwards because its multiplier is quite large.
I am not sure what the other force is supposed to be. You get the the normalized vector to the anchor point (reversed) but then you multiply it by the dot product with the velocity?… Is this supposed to be some kind of projection? (note that non of the vectors is normalized so the dot product will be |velocity| * |tether| * cos(angle) )
About the behavior definition… You need to be more deliberate with your design.
“…pull themselves up or down with W or S…” Doesn’t “pulling themselves down” mean that S will “move you back and extends the tether” as described.
What should A and D do while hanging on the line? What about if you are attached but still on the ground? What about if you anchor to a lower point like if you are on the edge of a canyon and attach at a lower point on the opposite wall so the tether pulls you down to the ground?
Wat happens if you just anchor and don’t push any button - not W, not S - will you stay on the same position? What about just pushing A and D while anchored? At what point is the tether removed and the link broken?